1. Field of the Invention
The present invention relates to a shoe, and more particularly to an improvement in a pattern of a bottom surface of the shoe.
2. Description of the Related Art
When hitting a golf ball, a golf player sets an address such that a line connecting right and left tiptoes is in almost parallel with a hitting direction. In an address for a right-handed golf player, a left foot is positioned on the front side in the hitting direction and a right foot is positioned on the rear side in the hitting direction. In the address, a head of a golf club is positioned close to a golf ball. In this state, the golf player starts take-back, pulls the head rearward and then swings the golf club upward. The highest position of the head swung upward is equivalent to a top position. In the top position, a downswing is started and the head is swung downward so that the head impacts the golf ball. After the impact, the golf player swings the golf club forward and then upward (follow-through). Thus, a finish is attained.
From the top position to the finish, the golf player carries out a body turn by setting a left foot as a pivot. At the same time, the golf player kicks the ground by a right foot to transmit the force to the golf ball. In other words, a right-handed golf player uses a left foot as a pivoting foot and a right foot as a kicking foot. To the contrary, a left-handed golf player uses a right foot as the pivoting foot and a left foot as the kicking foot.
From the top position to the finish, great force is applied to both feet of the golf player. In some cases, the force causes golf shoes to slip off from the ground. In which the slip is caused, a swing form is disordered so that a misshot is generated.
In order to attain slip prevention, a needle-like spike pin formed of metal or ceramics is provided on the bottom surfaces of the golf shoes. In such golf shoes, the slip is considerably prevented. However, there is a problem in that the spike pin damages a lawn on a green, a floor in a clubhouse and a road surface of a passage for walking which is provided in a golf course. Moreover, the golf shoes having the spike pin give a push-up feeling and are not comfortable for the golf player to wear. In recent years, the golf shoes having the spike pin have not been preferred for use.
Golf shoes having projections formed of rubber or synthetic resin which are provided on bottom surfaces in place of the spike pin have been proposed and spread. Such golf shoes rarely damage a lawn and are very comfortable to wear. In the golf shoes, however, there is a problem in that the projection has a smaller slip prevention performance than the spike pin.
The present inventor investigated a vector of force applied to feet from the top position to the impact (that is, a magnitude and a direction) and found the following. For a pivoting foot, force is roughly applied in almost a direction from a heel to a tiptoe. In detail, the force is mainly applied to a rear portion in the hitting direction of the foot in the top position (toward an inside for the pivoting foot of the golf player) and the direction is equivalent to a slightly rearward tiptoe direction. Depending on the progress of a swing, the position to which the force is mainly applied is transferred to the center of the foot, and then a front position (toward an outside for the pivoting foot of the golf player). Depending on the progress of the swing, the direction of the force is also transferred in a complete tiptoe direction, and then in a slightly forward tiptoe direction. It is supposed that these changes are caused by a body turn using a pivoting foot and the movement of a weight.
For a kicking foot, force is roughly applied in almost a direction from the tiptoe to the heel. In detail, the force is mainly applied to a front portion in the hitting direction of the foot in the top position (toward an inside for the kicking foot of the golf player) and the direction is also equivalent to a slightly forward heel direction. Depending on the progress of a swing, the position to which the force is mainly applied is transferred to the center of the foot, and then a rear portion (toward an outside for the kicking foot of the golf player). Depending on the progress of the swing, the direction of the force is also transferred in a complete heel direction, and then in a slightly rearward heel direction. It is supposed that these changes are caused by movement of a weight from the kicking foot to the pivoting foot at the time of the start of a downswing and the subsequent rotation of the kicking foot.
Japanese Laid-Open Patent Publication No. 2001-299406 has disclosed golf shoes which consider a difference in a role between a pivoting foot and a kicking foot. In the golf shoes, a projection is formed along a line to be convex in a tiptoe direction over a bottom surface of a shoe body for a pivoting foot and a projection is formed along a line to be convex in a heel direction over a bottom surface of a shoe body for a kicking foot. In a golf swing having such a very complicated movement pattern mixing a turning movement (body turn) and a translation movement, the golf shoes display an excellent slip prevention performance.
However, in the case in which the slip prevention is achieved by the projections having different patterns on left and right, it is necessary to prepare both the golf shoes for a right-handed golf player and a left-handed golf player and the burden of a cost is increased for golf shoe manufacturers. If the left-handed golf player wears golf shoes for the right-handed golf player or the right-handed golf player wears golf shoes for the left-handed golf player, there is also a problem in that the slip prevention is insufficient during a swing. There is also a problem in that a shoe body for a pivoting foot and a shoe body for a kicking foot in the golf shoes easily slip on upward and downward slopes respectively.
In consideration of these problems, the present inventor has proposed golf shoes in Japanese Patent Application No. 2000-235175 in which a double-side-slip-preventing projection including a tiptoe side slip prevention wall formed along a line to be convex in a tiptoe direction and a heel side slip prevention wall formed along a line to be convex in a heel direction is mainly formed. Also in the case in which any of right-handed and left-handed golf players wears the golf shoes, the double-side-slip-preventing projection suppresses the slip of a pivoting foot (a slip in almost the tiptoe direction) and the slip of a kicking foot (a slip in almost the heel direction) during a golf swing. In the golf shoes, it is not necessary to make left and right projection patterns different from each other.
In a portion (hereinafter referred to as a xe2x80x9ccontact pointxe2x80x9d) in which a line to be convex in the tiptoe direction and a line to be convex in the heel direction of the golf shoes come in contact with each other, two double-side-slip-preventing projections are opposed to each other with the contact point provided therebetween. In these cases, a heel side slip prevention wall of the double-side-slip-preventing projection positioned on the tiptoe side and a tiptoe side slip prevention wall of the adjacent double-side-slip-preventing projection positioned on the heel side are very close to each other and the tiptoe side slip prevention wall inhibits slip prevention effects from being produced by the heel side slip prevention wall, and the heel side slip prevention wall inhibits the slip prevention effects from being produced by the tiptoe side slip prevention wall. The slip prevention effects of the golf shoes are not always sufficient.
A shoe according to the present invention comprises an outsole body. A large number of projections formed of rubber or synthetic resin are provided on a bottom surface of the outsole body. Double-side-slip-preventing projections are mainly formed as the projections. The double-side-slip-preventing projection includes a tiptoe side slip prevention wall formed substantially along a line to be convex in a tiptoe direction and a heel side slip prevention wall formed substantially along a line to be convex in a heel direction. A space between two double-side-slip-preventing projections opposed to each other by interposing a portion in which the line to be convex in the tiptoe direction and the line to be convex in the heel direction come in contact with each other is set to be 2 mm or more.
The shoe comprises the double-side-slip-preventing projection, and furthermore, the space between the two double-side-slip-preventing projections opposed to each other with the contact point provided therebetween is sufficiently large. Also in the case in which force is applied in any direction, therefore, a slip can be suppressed.
It is preferable that a ratio of the number of contact points in which a space between two double-side-slip-preventing projections opposed to each other in the contact point is 2 mm or more to the total number of the contact points should be 5% or more. In such shoes, the slip can be more suppressed.
It is preferable that a ratio of the number of the double-side-slip-preventing projections to the total number of the projections should be 50% or more. In such shoes, the slip can be more suppressed.
It is preferable that an interior angle on a vertical section which is formed by the tiptoe side slip prevention wall and the outsole body should be 60 degrees or more. Moreover, it is preferable that an interior angle on a vertical section which is formed by the heel side slip prevention wall and the outsole body should be 60 degrees or more. In such shoes, the slip can be more suppressed.